Training Load compares your recent training stress to your longer-term baseline. Acute (7-day average TSS) reflects short-term fatigue; Chronic (28-day average TSS) reflects your established fitness. Balance is Chronic minus Acute - strongly positive means you're fresh, strongly negative means you're building fatigue faster than you're adapting. TSS itself comes from ride duration, power, and your current FTP estimate.

Rolling estimate from your hardest 20-70 min effort in the trailing ~90 days - a trend, not a single device-recorded value. Treat as approximate; a real 20-min FTP test is more accurate.